The recent image reading devices allow a user to set an image reading area such as by requesting the user to specify an image reading start position from which image reading is to be started and the lengths of an area to be read in the main scanning and sub-scanning directions. The image reading devices obtain image data of an area of an original document, which corresponds to the image reading area set by the user. The background image reading devices, however, start scanning the original document at its predetermined home position, mainly because the image reading devices need to read a reference whiteboard that is provided near the home position for further image processing. Since the background image reading devices start scanning the original document from the home position even when the image reading start position that is set by the user is away from the home position, it is not efficient in terms of productivity in image reading process.
In view of the above, Japanese Patent Application Publication No. 2003-234878 describes an image reading device, which changes a scan period in the main scanning direction according to the length of the image reading area in the main scanning direction. In case the image reading area set by the user is smaller than the maximum image reading area in length, the scan period in the main scanning direction is made shorter such that the scan speed in the sub-scanning direction increases, resulting in the increased productivity in image reading process. This image reading device, however, requires a complex structure, which tends to be costly, in order to interrupt reading operation in the main scanning direction.
Further, when the user sets up a specific image reading area through inputting various parameters to the image reading devices, the user may want to check beforehand whether the parameters input by the user actually reflects an image reading area of the original document that the user intends to select. Japanese Patent Application Publication No. 2002-111973 describes an image reading device, which allows the user to check the image reading area in both of the main and sub-scanning directions before scanning, by causing a light source to be partly turned on or off to indicate the image reading area specified by the user. In order to partly turn or off the light source, the light source is implemented by an array of lighting elements. For this reasons, it requires a complex structure, which tends to be costly, to control on or off of each of the lighting elements according to the image reading area set by the user.